Electron beam recording



2 Sheets-Sheet 1 Eiled May l5, 1953 ,III II /NI/E/I/ TOR H. G. WE HE ATTORNEV 2 Sheets-Sheet 2 nvvfvvrof? H G. WEHE ATTORNEY April 21, 1959 H.G. 'WEHE i ELECTRON BEAM RECORDING Filed May 15. 195s A United StatesPatent O ELECTRON BEAM RECORDING Herman G. Wehe, Summit, NJ., assignorto Bell Telephone Laboratories, Incorporated, New York, N.Y., acorporation of New York Application May 15, 1953, Serial No. 355,270

4 Claims. (Cl. 346-74) This invention relates to the recording ofphenomena or intelligence.

One general object of this invention is to facilitate the translation oftransient phenomena into permanent records. Another object of thisinvention is to enable such translation into invisible records which canbe revealed at any desired time, for example substantially concomitantlywith the translation or at relatively long times thereafter.

The invention involves broadly converting the phenomena or intelligenceto be recorded into radiation representative thereof, directing thatradiation upon the surface of a solid dielectric and depositing a filmof solid material upon the dielectric.

In accordance with one aspect of the invention, the revelation of therecorded phenomena may be accomplished substantially simultaneously withthe incidence of the radiation. The method thus practiced is especiallysuitable for the television art when utilizing a dielectric in the formof a transparent plastic strip for projecting on a larger scaleintelligence received from a distant station. For example, signals maybe received, recorded and immediately projected for viewing by largeaudiences. Additionally the method of this invention enables permanentrecording of such television transmissions. It is apaprent thatpermanent records may similarly be made of a variety of phenomena, forexample radar images, oscillograms, intelligence patterns generated byelectronic computers and the like.

In another aspect of this invention, the revelation of the recordedphenomena may be delayed for a prolonged period following the radiationstep. The method thereby enables latent recordings of intelligence whichmay be retained in unrevealed form until disclosure is desired.Revelation is then accomplished by the deposition of a solid material asmentioned above. These and other applications will be understood by theexposition of the invention hereinafter set forth.

According to one preferred method, the objects of this invention arerealized by employing a dielectric material, such as cellulose nitrate,in the form of a transparent plastic. Where translucence or opacity isdesired or where recording medium is too fragile for self support, asupporting medium such as Kraft capacitor paper coated with cellulosenitrate lacquer may be utilized. The recording beam, for example from acathode ray gun, is impinged upon the dielectric following which solidmaterials in vaporized form, for example silver and zinc, are depositedsuccessively upon the surface of the dielectric. Typically, the initialfilm of one material is of such thinness as to be invisible while thesucceeding layer of material is heavier and discloses or develops therecorded phenomena. The vapor deposition steps of the process may beadvantageously performed within a vacnum.

The methods may be carried out as a continuous process in which thedielectric material in strip form is subjected successively to the abovedescribed steps.

2,883,2571 Patented Apr. 2l, 1959 ICC Methods of carrying out the vapordeposition steps suitable for the practice of this invention within avacuum are Idescribed in application Serial No. 316,928 by D. A. McLeanand H. G. Wehe, filed October 25, 1952, now Patent No. 2,754,230.

The invention will be more fully understood from the followingdescription taken in connection with the drawing in which:

Fig. 1 is a diagram of one form which the process in accordance with theinvention may take;

Fig. 2 is a diagram of another form which the process in accordance withthe invention may take; and

Fig. 3 is a perspective schematic View of illustrative Iapparatus forpractising the methods in accordance with this invention.

Referring to Fig. 1, the recording process begins with the -dielectricmaterial in dry unexposed form. In addition to cellulose nitratepreviously mentioned, other dielectric materials may be employed. Forexample, other organic solids such as cellulose acetate, celluloseacetate butyrate, polystyrene, polyethylene terephthalate,ethylcellulose, and regenerated cellulose have been found satisfactory.These dielectric materials, including cellulose nitrate, are obtainableas transparent plastics, a particularly useful form for practicing themethod of this invention. Additionally, recording may be accomplished indielectric lacquers coated on supporting dielectric materials. Forexample, lacquers composed of any one of the compounds; cellulosenitrate, cellulose acetate, cellulose acetate butyrate, or polystyrene,in solution, coated on dielectric paper and thoroughly dried aresusceptible to the recording method herein described.

As depicted in Fig. 3, the dielectric may be utilized advantageously instrip form gathered in a roll 210` which may be fed continuously from amandrel 11 and passed over a series of rolls 12 to a final Windingmandrel 13 driven by an electric motor 14 through gears 15 and 16. Therecord-bearing material is thus gathered in a roll 17 on the mandrel 13.

Step II comprises the recording of the desired phenomena and asillustrated in Fig. 3 may be accomplished by directing the beam from acathode ray gun 1S upon the dielectric strip 19 and the backing plate 20juxtapositioned thereto.

In the apparatus, the phenomena to be recorded exist in the form of orare converted into an electrical signal which is applied to thedeflection plates 21 or control electrode 30, or both of the cathode raygun 18. The emission of the energized gun forms a beam which impingesupon the surface of the dielectric. As is well known in the art, thesignal impressed upon the control and deecting electrodes isdeterminative of the form and intensity of the pattern traced upon thetarget surface. Thus the trace upon the dielectric surface correspondsin instantaneous position to one parameter of the signal as representedby the potential or potentials applied between the deflection plates.The intensity of the beam may be controlled in accordance with anotherparameter of the signal as represented by a voltage applied to thecontrol electrode.

Where the recorded trace consists merely of a continuous curvilinearligure representing functions of time and amplitude, only one set ofdellecting electrodes need be used if the dielectric strip is moved atuniform speed. Where complete images are recorded as in the televisionart, complete beam control may be utilized and the dielectric materialmomentarily remains stationary for the period during which a completeimage is traced or the motion of the dielectric may be substituted forone sweep parameter. The recorded trace is invisible at this juncture.The backing plate 20 functions as a target or collecting plate for thebeam.

The process is continued in step III during which the dielectricmaterial is coated advantageously with a lm of extreme thinness as *byvapor deposition from an energized molybdenum filament loaded withsilver. This film is of such thinness as to be invisible, say less thanten angstroms. Considering the dielectric surface generally, thisinitially deposited lm is approximately of the order of magnitude of amonolayer. As depicted in Fig. 3, the filament 23 is heated yby thebattery 24 causing the silver to vaporize from which condition itdeposits selectively upon the strip 26. In the method of Fig. 1 thedeposited silver is invisible.

The enclosure 2S indicated in dotted outline provides a mask whichprevents dissipation of the silver vapor which otherwise would coat theentire apparatus. This silver deposition step may be carried out over anarea of the strip which is simultaneously being subjected to theimpingement of the electron beam.

As represented herein, deposition of the solid material occurs on thesame surface previously or simultaneously subjected to the electronbeam. However, phenomena have been recorded on dielectrics of thelacquered paper group by simultaneously or subsequently depositing thesolid material upon the reverse surface from that subjected to therecording ibeam. Advantageously, the radiation is irnpinged upon thelacquered side of the coated paper dielectrics. Where the above-notedreverse plating method is used, recordings have been made with the papersurfaces interchanged; that is, in one case irradiating the lacqueredsurface and plating the paper surface, and in the other irradiating thepaper surface and plating the Vlacquered surface.

The succeeding step denoted is IV in Fig. 1 comprises the vapordeposition of a heavier layer of coating material directly upon theinitially deposited film. This revealing layer may be from 50 to 1,000angstroms thick depending upon the desired degree of contrast. This isaccomplished by passing the dielectric strip near the coilheatedCrucible 27 lled with zinc. As in the case of the silver depositionapparatus, the zinc vaporizing equipment is masked by an enclosure 28.Alternatively, in the case of the method of Fig. 2, the heavier layer ofcoating material may consist of additional silver deposited from theloaded molybdenum filament omitting the zine deposition step. Bysubjecting the dielectric material to the silver vapor until thedeposited layer has `a thickness of the order of 40 angstroms or more,the recorded phenomena will be revealed therein without the depositionof a separate layer of different material such as zinc. A generally moreadvantageous control of results is attained by the utilization ofdiierent materials in the successive layers. Generally, better imagesare obtained also in the case of the opaque dielectrics where both beamimpingement and vapor deposition occur on the lacquered side.

It is to be noted generally that the form of apparatus herein describedfor accomplishing the method of this invention is particularly suitablewhere immediate projection of the recorded phenomena is desired.Deposition of the initial lm, step III, may occur simultaneously withthe radiation step, the moving dielectric strip passing rapidly on toreceive the heavier layer which reveals the recorded image. Where thedielectric strip is a transparent plastic such image may be immediatelyprojected by conventional and well-known methods. Also projection may beby reection from an opaque surface.

It is to be understood that certain modes of radiation should be carriedout within an evacuated space. For example, the electron beam recordingstep of the specific method herein described should occur within .avacuum.

Other radiation methods may be used to record phenomena underatmospheric conditions (in a vacuum, or at greater than atmosphericpressure). For example, ultra-violet light in beam or flood form willenable recording. Where ultra-violet flood lighting is employed thedielectric is masked to produce the desired recorded image. Ion beamslikewise lend themselves to radiation recording in air at normalpressure. Generally, ultraviolet and ion recording is not as rapid aselectron beam recording.

A vacuum envelope 29 is indicated as enclosing the entire apparatus ofFig. 3. Within such envelope maintenance of maximum absolute pressure ofthe order of 1x10-4 mm. of mercury has been found advantageous. Wheresuch an atmospheric control enclosure is provided, it is possible alsoto affect the degree of background plating by utilizing pure gases suchas hydrogen and oxygen in place of residual air. For example, whereelectron beam recording is carried out using capacitor paper coated withcellulose acetate lacquer, a hydrogen atmosphere retards plating in theimage ydeveloped by silver `and zinc deposition. Conversely a residualoxygen atmosphere enhances plating with the same materials.

Blocks IIA and IIIA of Fig. 1 and block IIA of Fig. 2 indicatealternative procedures by which the dielectric material may betemporarily withdrawn from the process before revelation of therecording. Whether this interruption of the process occurs at IIA orIIIA, the recorded phenomena are invisible. Withdrawal at IIIA, however,following the thin layer coating presents the greater desirability :fromthe standpoint of stability of the recorded matter.

'Ihe underlying reason for the above-described process has not beenfully established. It is established, however, that the radiation towhich the dielectric is subjected so affects the dielectric as to causethe initially deposited lm of material to adhere only in certain areasin accord- 'ance with the radiation pattern.

Why the initial invisible film deposits sometimes more heavily over theirradiated and sometimes over the nonirradiated areas of the dielectricis not known exactly. Generally, however, in the case of electron beamrecording the appearance of the image may be varied by varying thethickness of the initial iilm Within the limits of invisibility. Forexample, using cellulose acetate and cellulose acetate butyrate forrecording, the -beam trace as finally revealed by zinc deposition isdark on a light background (viewed with transmitted light) when a smallamount of silver is used. Increasing the amount of silver causes thetrace to appear light on a dark background. Such reversal effect doesnot occur when the dielectric is cellulose nitrate upon which the beamtrace is constantly light on a dark background. Irrespective of materialand amount of deposition, the shading of the recorded phenomena is alsoa function of the recording beam intensity as has been noted above. Theuse of silver and zinc as deposition material results in recordingshaving the general black-and-white appearance of photographic negativesand positives.

The readiness with which the dielectric accepts the initially-depositedmaterial may be termed the accommodation coefficient of the dielectric.The recording radiation then may be considered as producing amodification of the accommodation coecient in accordance with thephenomena being recorded. This modication then leads to the differencein the deposition or sticking rate of the initial layer of material.

Indications are that the initial film which is ordinarily invisiblefurnishes the nuclei or seeds upon which the heavier revealing coatinggrows, in a manner somewhat analogous to the initiation of crystalgrowth in a supersaturated solution. Hence, the materials of which thecoating ilms may be composed are defined in some degree 4by thefunctions which they perform.

In a broad aspect, therefore, the deposited coatings may be composed ofnormally solid materials which may be vaporized without suxeringconsequent decomposition. Generally, the initial lilm may be composed ofmaterials which recognize the modified accommodation coefncient of thedielectric and will deposit diterentially in accordance thereto. Suchinitial lm materials also provide the seeds or nuclei for the succeedinglayer and hence are said to have the property of easy nucleation. Silverand copper are representative of satisfactory initial lm materials.

Because the revelation of the recorded phenomena in the heavier coatingappears to result from the adherence of the particles of this layer tothe seeds or nuclei of the initial layer they should have poornucleation properties. In other Words, materials used for the revealingcoating should not deposit well on the untreated dielectric from a lowvapor concentration. Zinc and cadmium are representative of materialsfulfilling the requirements for heavier coating materials.

While the above is believed to be a correct explanation of certainprinciples underlying applicants invention it is to be understood, ofcourse, that the invention is independent of any theory Which may beadvanced to account for the results obtained.

Desirable results have been obtained using a cathode ray gun of theelectrostatic deflection type with the cathode positioned about liveinches from the recording surface with the backing plate one-half inchbehind the dielectric strip. Under such conditions it has been foundadvantageous to utilize a grounded backing plate with the cathode of thegun at high negative potential, say of the order of 700 volts, while theplating machinery is maintained at positive potential. Recording may befacilitated for certain purposes by employing diierent velocities forthe strip in its travel through the apparatus. Such velocities may rangefrom zero velocity to greater than 800 feet per minute.

It is to be understood that the above-described arrangements areillustrative of the principles of this invention. Numerous otherarrangements may be devised by those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. The method of recording phenomena which comprises projecting anelectron beam against a surface of a thin sheet of dielectric selectedfrom the group consisting of cellulose nitrate, cellulose acetate,cellulose acetate butyrate, polystyrene, polyethylene terephthalate,ethylcellulose, and regenerated cellulose, varying the point ofincidence of said beam in accordance with a parameter of said phenomena,placing said sheet of dielectric in storage for a period of time,removing said sheet of dielectric from storage, vapor depositing aninvisible lm of metal selected from the group consisting of silver andcopper on said dielectric surface, and applying by vapor deposition onsaid film a visible permanent coating of a metal selected from the groupconsisting of zinc and cadmium.

2. The method of recording phenomena which comprises projecting anelectron beam against a surface of a thin sheet of dielectric selectedfrom the group consisting of cellulose nitrate, cellulose acetate,cellulose acetate butyrate, polystyrene, polyethylene terepnthalate,ethylcellulose, and regenerated cellulose, varying the point ofincidence of said beam in accordance with a parameter of said phenomena,vapor depositing an invisible iilm of metal selected from the groupconsisting of silver and copper on said dielectric surface, placing saidsheet tof dielectric in storage for a period of time, removing saidsheet of dielectric from storage, and applying by vapor deposition onsaid film a visible permanent coating of a metal selected from the groupconsisting of zinc and cadmium.

3. An apparatus for making a visual record for phenomena comprising, incombination, a sheet of dielectric material, means for projectingradiation representative of said phenomena upon said sheet, saidprojecting means comprising an electron gun, first means for vapordepositing on said dielectric sheet an invisible iilm of a metalselected from the group consisting of silver and copper, and secondmeans separated from said rst means for vapor depositing a coating of ametal selected from the group consisting of zinc and cadmium upon saiddielectric sheet, and means comprising at least one motordriven rollerfor moving said dielectric sheet successively past said projectingmeans, said iirst vapor depositing means, and said second vapordepositing means.

4. Apparatus in accordance with claim 3 in which said sheet ofdielectric material is one selected from the group consisting ofcellulose nitrate, cellulose acetate, cellulose acetate butyrate,polystyrene, polyethylene terephthalate, ethyl-cellulose, andregenerated cellulose.

References Cited in the tile of this patent UNITED STATES PATENTS2,143,214 Selenyi Jan. 10, 1939 2,200,741 Gray May 14, 1940 2,221,776Carlson Nov. 19, 1940 2,239,452 Williams et al Apr. 22, 1941 2,281,638Sukumlyn May 5, 1942 2,384,500 Stoll Sept. 11, 1945 2,431,923 DimmickDec. 2, 1947 2,478,681 Beers Aug. 9, 1949 2,551,582 Carlson May 8, 19512,616,961 Groak Nov. 4, 1952 2,709,663 McLean May 31, 1955 2,716,048Young Aug. 23, 1955 FOREIGN PATENTS 817,447 France May 24, 1937

